Pertaining to the extreme north of the earth, or (usually jocular) to a specific northern country or area.

1633, C. Butler

The hyperborean or frozen sea.

1922, James Joyce, Ulysses:

You could have knelt down, damn it, Kinch, when your dying mother asked you, Buck Mulligan said. I’m hyperborean as much as you. But to think of your mother begging you with her last breath to kneel down and pray for her. And you refused.